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    SubjectRe: [RFC PATCH v3 06/37] bpf tools: Introduce 'bpf' library to tools


    在 2015/5/19 1:35, Alexei Starovoitov 写道:
    > On 5/17/15 3:56 AM, Wang Nan wrote:
    >> This is the first patch of libbpf. The goal of libbpf is to create a
    >> standard way for accessing eBPF object files. This patch creates
    >> Makefile and Build for it, allows 'make' to build libbpf.a and
    >> libbpf.so, 'make install' to put them into proper directories.
    >> Most part of Makefile is borrowed from traceevent. Before building,
    >> it checks the existance of libelf in Makefile, and deny to build if
    >> not found. Instead of throw an error if libelf not found, the error
    >> raises in a phony target "elfdep". This design is to ensure
    >> 'make clean' still workable even if libelf is not found.
    >>
    >> Signed-off-by: Wang Nan <wangnan0@huawei.com>
    >> ---
    > ...
    >> +
    >> +# Version of eBPF elf file
    >> +FILE_VERSION = 1
    >
    > what that comment suppose to mean?
    >
    >> +# Makefiles suck: This macro sets a default value of $(2) for the
    >> +# variable named by $(1), unless the variable has been set by
    >> +# environment or command line. This is necessary for CC and AR
    >> +# because make sets default values, so the simpler ?= approach
    >> +# won't work as expected.
    >
    > what this for? copy-paste?
    >
    >> +# Allow setting CC and AR, or setting CROSS_COMPILE as a prefix.
    >> +$(call allow-override,CC,$(CROSS_COMPILE)gcc)
    >> +$(call allow-override,AR,$(CROSS_COMPILE)ar)
    >
    > was cross-compile tested or just copy-pasted?
    >

    Cross compiling is tested on aarch64.

    >> +EXT = -std=gnu99
    >
    > I guess it was copy-pasted from libtraceevent, but please double
    > check that it's actually needed.
    >

    Will remove.

    >> +# Append required CFLAGS
    >> +override CFLAGS += -fPIC
    >> +override CFLAGS += $(INCLUDES)
    >> +override CFLAGS += -D_GNU_SOURCE
    >
    > _GNU_SOURCE actually needed?
    > Please sanitize the file.
    >
    >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
    >> new file mode 100644
    >> index 0000000..bebe99a
    >> --- /dev/null
    >> +++ b/tools/lib/bpf/libbpf.c
    >> @@ -0,0 +1,15 @@
    >> +/*
    >> + * common eBPF ELF loading operations.
    >> + *
    >> + * Copyright (C) 2015, Wang Nan <wangnan0@huawei.com>
    >> + * Copyright (C) 2015, Huawei Inc.
    >
    > since it borrows heavily from samples/bpf/bpf_load.c, libbpf.h
    > would be nice if you mention the source and/or copyright in the header.
    >

    Will change. Could you please provide copyright information so I can add
    it here?

    >> + *
    >> + * Released under the GPL v2. (and only v2, not any later version)
    >> + */
    >
    > are you sure about this restriction? libtracevent is LGPL, for example.
    >

    Will change.

    Thank you.




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